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Bug 1967605

Summary: Enable interrupt based asynchronous page fault mechanism by default
Product: Red Hat Enterprise Linux 9 Reporter: Vitaly Kuznetsov <vkuznets>
Component: qemu-kvmAssignee: Vitaly Kuznetsov <vkuznets>
qemu-kvm sub component: Machine Types QA Contact: liunana <nanliu>
Status: CLOSED CURRENTRELEASE Docs Contact:
Severity: unspecified    
Priority: unspecified CC: chayang, coli, ddepaula, jinzhao, juzhang, mrezanin, virt-bugs, virt-maint
Version: 9.0Keywords: FutureFeature, TestOnly, Triaged
Target Milestone: betaFlags: pm-rhel: mirror+
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: qemu-kvm-6.0.0-7.el9 Doc Type: Enhancement
Doc Text:
Story Points: ---
Clone Of: 1967603 Environment:
Last Closed: 2021-12-07 22:10:18 UTC Type: Feature Request
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1967603    

Description Vitaly Kuznetsov 2021-06-03 13:09:31 UTC 
+++ This bug was initially created as a clone of Bug #1967603 +++

RHEL-8.4 disabled traditional asynchronous page fault mechanism and added a new one (interrupt based asynchronous page fault) which can be enabled with 'kvm-asyncpf-int' CPU option. The new mechanism is, however, not enabled by default as upstream QEMU supports kernels which don't have it. Downstream, we should be good as RHEL kernels starting with 8.4 have the required bits.
Comment 3 liunana 2021-07-05 11:14:54 UTC 
Test Environments:
    intel-whitley-02.khw1.lab.eng.bos.redhat.com
    qemu-kvm-6.0.0-7.el9.x86_64
    5.13.0-0.rc7.51.el9.x86_64

Test steps:
1. Boot guest with '-machine pc-q35-rhel8.5.0', check guest's dmesg.
# dmesg | grep async
dmesg | grep async
[    0.019210] kvm-guest: setup async PF for cpu 0
[    0.186264] kvm-guest: setup async PF for cpu 1
[    0.189262] kvm-guest: setup async PF for cpu 2
[    0.192261] kvm-guest: setup async PF for cpu 3
[    0.196260] kvm-guest: setup async PF for cpu 4
[    0.198263] kvm-guest: setup async PF for cpu 5
[    0.201260] kvm-guest: setup async PF for cpu 6
[    0.204260] kvm-guest: setup async PF for cpu 7

2. check 'Hypervisor callback interrupts' inside guest.
# grep Hyp /proc/interrupts
grep Hyp /proc/interrupts
HYP:          1          1          1          1          1          1          1          1   Hypervisor callback interrupts


3. check 'Hypervisor callback interrupts' inside guest while using the swap on host.
On host:
]# free -h
               total        used        free      shared  buff/cache   available
Mem:            31Gi       8.1Gi        22Gi       1.0Mi       119Mi        22Gi
Swap:           15Gi       9.2Gi       6.4Gi

Inside guest.
# grep Hyp /proc/interrupts
HYP:          1          1          3          1          1          1          1          1   Hypervisor callback interrupts




Move to verified according to above tests, thanks.


Best regards
Liu Nana